Weka Forecast Help

Hello guys,
First of all I would like to apologize for my English mistakes, It's not my first language.
Anyways, I'm trying to use the Weka's Forecast to make a prediction of some data for the next few days. It will be like that:

It is working, I can choose how many days I'll predict and which algorithm I want. However, I would like to use only one ARFF file to do more than one prediction. I want to predict more than one machine without relation between them.
For example:

But I'm having two problems: 1) I can't use the same Date on my Data. 2) I think The Forecast function doesn't work with non-numerical values.
My questions are: how can I deal with those problems? Is that any other software that I could use to work with a bunch of machines at the same time ? Is there any other function on Weka that I could use ??
thanks for everything!